Adhesive compositions and method for selection thereof

ABSTRACT

Adhesive compositions and a method for selecting adhesive compositions are disclosed herein. Preferred adhesives generally have small domains and/or a homogeneous domain distribution. The method of selecting adhesives is based on size and distribution of the domains.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Provisional Patent ApplicationNo. 60/456,393, filed Mar. 30, 2003, the disclosure of which isincorporated by reference.

FIELD OF THE INVENTION

This invention relates to adhesives and methods for selecting adhesivesbased on their adhesive phase structures or properties. Applicantsbelieve that the bulk and surface adhesive phase structures are relevantin determining the adhesive performance and that methods for determiningthe accurate meso-scale phase structures are relevant for determiningthe performance of adhesives.

BACKGROUND

Adhesives can be made in many forms. Many adhesives are made fromrelatively high molecular weight polymers mixed with low molecularweight tackifying resins. They may or may not be further combined withother components such as oil or wax to control properties such asviscosity at application temperature, adhesive open time, and set time.

Polymers supply many of the basic adhesive properties such as cohesionand elongational and elastic behaviors. Relatively low molecular weightresins (usually with number average molecular weights (Mn) ranging from300 to 2000) are useful in adhesive applications. When combined withpolymers such as those described above, these low molecular weightresins decrease the entanglement density of the polymer chains, whichimproves the adhesive properties. Tackifiers also have relatively highglass transition temperatures (Tg) for such low molecular weightamorphous materials. The Tg is typically from below 0° C. to about 90°C. Tackifiers interact with the polymer chains and associate with theamorphous polymer phases at the desired operating temperatures;therefore, good compatibility and dispersion is desired for advantageousperformance.

Other components are often used and dispersed in the adhesive matrix.Waxes are often used in hot-melt adhesives (HMAS) to lower viscosity atthe application temperature and to decrease the set time of the adhesivebond. The waxes crystallize rapidly resulting in a step-change inviscosity during cooling and preventing movement of the bond. For goodadhesion, the wax crystals are preferably as small as possible andpreferably do not form a wax surface layer on the adhesive.

It is desirable to keep a continuous polymer phase in the bulk phase toenable elongation of the matrix under stress. If this is not done, theadhesive may break at very short extensions and not be able to absorbthe energy during bond deformation. It is therefore desired to have anadhesive having small and/or homogeneously distributed domains asdescribed herein.

Good surface phase structures or domains are also desirable. Manyadhesives have good adhesion to certain substrates but not to others.For example, some adhesives do not exhibit high all-around performanceon polar surfaces, such as polyethylene terephthalate (PET), acrylicvarnishes or low energy surfaces such as polyethylene or fluorinatedsubstrates. The adhesive industry recognizes this problem but has yet toachieve a solution. Background references include U.S. Pat. Nos.4,554,304, 4,719,260, WO 03/025036, WO 03/025037, WO 03/025038, WO03/025084, JP 52 090535 A, and EP 0 803 559 A.

Thus, a need exists for optimum adhesives that achieve good adhesiveperformance regardless of the substrate. There also exists a need for amethod to determine which adhesive compositions might be candidates forexcellent performance on multiple substrates.

While not wishing to be bound by any theory, Applicants believe thatadhesive performance, including the debonding process, is dependent onthe phase structures (also referred to herein as domains) in the bulk ofthe adhesive and on the surface of the adhesive. When the pull-off forcedomains or stiffness domains are below a certain area and/or have a goodhomogeneous domain distribution, the overall adhesive performance isbelieved to be better.

SUMMARY

A method is disclosed for selecting an adhesive composition havingimproved performance, the method comprising observing a surface using anatomic force microscope wherein the surface is a non-destructivelyde-bonded surface of the adhesive composition. The method comprises (a)subdividing the de-bonded surface into domains as defined herein ofpull-off force or stiffness; and, (c) selecting an adhesive compositionhaving:

-   -   (i) an average stiffness domain area≦about 2500 nm²; or    -   (ii) an average pull-off force domain area≦about 2500 nm²; or    -   (iii) an pull-off force overall average domain distribution less        than about 25%; or    -   (iv) a stiffness overall average domain distribution less than        about 25%; or    -   (v) combinations of any two or more thereof.

Also disclosed herein are adhesive compositions meeting any one or moreof the above parameters (i)–(v), articles comprising an adhesivecomposition meeting any one or more of the above parameters, the use ofany such compositions, the use of tackifiers to control the size (area)of the stiffness and/or pull-off force domains and/or the distributionsof these domains as described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1–6 are Pulse Force Microscopy (PFM) images illustrating thepull-off force domain areas, stiffness domain areas, pull-off forcedomain distributions and/or the stiffness domain distributions forExamples 1–3 described herein.

FIGS. 7–12 are Atomic Force Microscopy (AFM) images generated in“tapping mode.” FIGS. 7, 9, and 11 illustrate topographical images, andFIGS. 8, 10, and 12 illustrate phase shift images.

FIGS. 13–16 are images derived during image processing and illustratethe low intensity domains and the high intensity domains found in eachof FIGS. 3 and 4 at the image processing steps indicated below.

DETAILED DESCRIPTION

General Definitions

It is possible to use different techniques to determine the phase/domainstructures, but Atomic Force Microscopy (AFM) is preferred. A relativelyrecently developed offshoot of AFM, Pulse Force Microscopy (PFM), iseven more preferable, and was used to analyze the adhesive compositionsin the examples.

As used herein, high stiffness domains and low stiffness domains areareas within the adhesive matrix defined by PFM stiffness imaging.

As used herein, high pull-off force (or adhesion) domains and lowpull-off force (or adhesion) domains are areas within the adhesivematrix defined by PFM adhesion imaging.

A domain is a region or area within an overall adhesive matrix whereinthere is the same physical property (e.g., pull-off force, stiffness)around which there is a difference in this property. For example,differences in pull-off force or stiffness within the adhesive matrixoccur where there are regions of high pull-off force or stiffnessvarying to regions of low pull-off force or stiffness. Average domainareas within a given adhesive matrix are calculated as described below.

For example, FIGS. 2, 4 and 6 show gray-scale PFM stiffness imagescorresponding to Examples 1, 2 and 3 herein. In the Figures, the lighterthe region, the higher the stiffness and the darker the region, thelower the stiffness. Comparing FIGS. 2, 4 and 6, the formulationcontaining Tackifier 3 (FIG. 6, Example 3) gives larger, fewer domainswith low stiffness and larger, fewer domains with high stiffness, andthe distribution of these domains is not homogeneous across the imagefield. The formulation with Tackifier 2 (FIG. 4, Example 2) has smallerdomain sizes and more evenly distributed throughout the image field, andconsequently it gives better adhesive performance. The formulationcontaining Tackifier 1 (FIG. 2, Example 1) has the smallest and mosthomogeneously distributed stiffness domains and gives the best adhesiveperformance. Similar analyses hold true for the pull-off force domainsgenerated in corresponding FIGS. 1, 3 and 5.

Because there is almost always a continuous transition region from onestiffness/pull-off force region to another, it is preferred to assignboundaries to these regions for the purpose of quantifying their sizesto clarify the differences between adhesives and to determine how thesestructures/domains affect the adhesive properties. The method forassigning the transition regions, and hence the size, area anddistribution of the domains, is described below. The analyticaltechniques described herein determine the sizes or areas of the domainsby analyzing two-dimensional images, and therefore area measurements aregiven.

Molecular weights (number average molecular weight (Mn), weight averagemolecular weight (Mw), and z-average molecular weight (Mz)) are measuredby Size Exclusion Chromatography using a Waters 150 Gel PermeationChromatograph equipped with a differential refractive index detector andcalibrated using polystyrene standards. Samples are run intetrahydrofuran (THF) at a temperature of 45° C. Molecular weights arereported as polystyrene-equivalent molecular weights and are generallymeasured in g/mol.

Saponification number, as used herein, was measured according to thefollowing procedure. 2 g of powdered resin material to be evaluated wasdissolved in 25 ml toluene/isopropanol (1:1 wt ratio) and 50 ml of 0.1Nalcoholic KOH was added by pipette. After refluxing for 30 min andcooling to room temperature the solution was titrated against 0.1N HClusing phenolphthaleine indicator. A blank run was carried out withoutresin material. Saponification number (mg KOH/g resin) was thencalculated by multiplying 56.1 (approximate molecular weight ofKOH)×volume of standard HCl×Normality of HCl divided by the weight ofresin material sample.

Aromatic content and olefin content are measured by ¹H-NMR as measureddirectly from the ¹H NMR spectrum from a spectrometer with a fieldstrength greater than 300 MHz, most preferably 400 MHz (frequencyequivalent). Aromatic content is the integration of aromatic protonsversus the total number of protons. Olefin proton or olefinic protoncontent is the integration of olefinic protons versus the total numberof protons.

Adhesive Compositions

Disclosed are adhesive compositions and methods for selecting adhesivecompositions. Adhesive compositions have stiffness domains, pull-offforce domains, a stiffness domain distribution, and a pull-off forcedomain distribution. When the adhesive comprises a wax, the adhesive mayalso have an average wax crystal size and a wax crystal sizedistribution. As previously noted, these parameters are useful inassessing adhesive performance and selecting adhesives based on theseparameters. Preferred adhesives meet the following parameters,preferably when adhered to and non-destructively de-bonded from asurface:

-   -   (i) an average stiffness domain area≦about 2500 nm²; or    -   (ii) an average pull-off force domain area≦about 2500 nm²; or    -   (iii) a pull-off force domain distribution less than about 25%;        or    -   (iv) a stiffness domain distribution less than about 25%; or    -   (v) combinations of any two or more thereof.

Preferred compositions possess at least two of parameters (i) through(iv), more preferably at least three of parameters (i) through (iv), andmost preferably all four of parameters (i) through (iv). Combinations ofone, two, three or four of parameters (i) through (iv) in any of thepreferred ranges of such parameters as described below are also withinthe scope of the invention.

In a preferred embodiment the surface is e.g., PTFE,polyethylene-co-tetrafluoroethylene, or other fluorinated surface, whendetermining the parameters. Preferably, the fluorinated surface issmooth.

It is believed that the average stiffness domain area, average pull-offforce domain area, stiffness domain distribution, and pull-off forcedomain distribution can be controlled by the selection of particularcomponents within an adhesive, e.g., selection of particular tackifiersin combination with a particular polyolefin and/or wax, to achieve theaforementioned parameters.

The stiffness domains of the adhesives or articles comprising anadhesive layer preferably have an average stiffness domain area≦about2500 nm², more preferably≦about 2400 nm², more preferably≦about 2300nm², more preferably≦about 2200 nm², more preferably≦about 2100 nm²,more preferably≦about 2000 nm², more preferably≦about 1900 nm², morepreferably≦about 1800 nm², more preferably≦about 1700 nm², morepreferably≦about 1600 nm², more preferably≦about 1500 nm², morepreferably≦about 1400 nm², more preferably≦about 1300 nm², morepreferably≦about 1200 nm², more preferably≦about 1100 nm², morepreferably≦about 1000 nm², more preferably≦about 900 nm², morepreferably≦about 800 nm², more preferably≦about 700 nm², morepreferably≦about 600 nm², more preferably≦about 500 nm², morepreferably≦about 400 nm², more preferably≦about 300 nm², morepreferably≦about 200 nm², and more preferably≦about 100 nm², whereinsuitable ranges comprise the combination of any two limits in thisparagraph.

The pull-off force domains of the adhesives or articles comprising anadhesive layer preferably have an average pull-off force domainarea≦about 2500 nm², more preferably≦about 2400 nm², morepreferably≦about 2300 nm², more preferably≦about 2200 nm², morepreferably≦about 2100 nm², more preferably≦about 2000 nm², morepreferably≦about 1900 nm², more preferably≦about 1800 nm², morepreferably≦about 1700 nm², more preferably≦about 1600 nm², morepreferably≦about 1500 nm², more preferably≦about 1400 nm², morepreferably≦about 1300 nm², more preferably≦about 1200 nm², morepreferably≦about 1100 nm², more preferably≦about 1000 nm², morepreferably≦about 900 nm², more preferably≦about 800 nm², morepreferably≦about 700 nm²more preferably≦about 600 nm², morepreferably≦about 500 nm², more preferably≦about 400 nm², morepreferably≦about 300 nm², more preferably≦about 200 nm², and morepreferably≦about 100 nm², wherein suitable ranges comprise thecombination of any two limits in this paragraph.

The pull-off force overall average domain distributions are preferablyless than about 25%. More preferably the distributions are less thanabout 20%, more preferably less than about 19%, more preferably lessthan about 18%, more preferably less than about 17%, more preferablyless than about 16%, more preferably less than about 15%, morepreferably less than about 14%, more preferably less than about 13%,more preferably less than about 12%, more preferably less than about11%, more preferably less than about 10%, more preferably less thanabout 9%, more preferably less than about 8%, more preferably less thanabout 7%, more preferably less than about 6%, more preferably less thanabout 5%, more preferably less than about 4%, more preferably less thanabout 3%, more preferably less than about 2%, and more preferably lessthan about 1%, wherein suitable ranges comprise the combination of anytwo limits in this paragraph.

The stiffness overall average domain distributions are preferably lessthan about 25%. More preferably the distributions are less than about20%, more preferably less than about 19%, more preferably less thanabout 18%, more preferably less than about 17%, more preferably lessthan about 16%, more preferably less than about 15%, more preferablyless than about 14%, more preferably less than about 13%, morepreferably less than about 12%, more preferably less than about 11%,more preferably less than about 10%, more preferably less than about 9%,more preferably less than about 8%, more preferably less than about 7%,more preferably less than about 6%, more preferably less than about 5%,more preferably less than about 4%, more preferably less than about 3%,more preferably less than about 2%, and more preferably less than about1%, wherein suitable ranges comprise the combination of any two limitsin this paragraph.

It is preferred to keep a continuous polymer phase in the bulk phase toenable elongation of the matrix under stress. If this is not done, theadhesive may break at very short extensions and not be able to absorbthe energy during bond deformation. It is therefore desired to have anadhesive having small and/or homogeneously distributed domains.Preferably, the adhesive compositions have average stiffness domainareas in any one of the preferred ranges listed above and a stiffnessdomain distribution within any one of the preferred ranges listed above.Preferably the adhesive compositions have average pull-off force domainareas in any one of the preferred ranges listed above and a pull-offforce domain distribution within any one of the preferred ranges listedabove.

Many adhesive composition embodiments may further comprise a wax. Wax isan adhesive component that is added to alter high temperature viscosityand decrease the setting time as the adhesive cools. Wax is normallymostly paraffinic or polyethylene-like in nature, but it can befunctionalized if desired. Wax crystals form rapidly and grow throughoutthe adhesive matrix. This produces a step-change in effective viscosityand prevents the applied adhesive bond from failing. Unfortunately, thesolid wax crystals can have two detrimental effects. First, if they growtoo large they can inter-lock and severely reduce the elongationalproperties of the bulk adhesive. Second, if they grow preferentially onthe surface of the adhesive, they can hinder the adhesive attractions ofthe adhesive. It is therefore preferred to reduce the wax crystal sizesand inhibit their effect on the surface. AFM can also be used toinvestigate the wax crystal structures. The methods disclosed herein formeasurement of domain areas are also useful for evaluatingwax-containing adhesive materials. It is preferred, however, to removethe wax from the formulation by conventional methods and evaluate theadhesive without the wax. With the wax present, views of the details ofthe domains may be obscured during the AFM or PFM analysis. It isbelieved, however, that the method of evaluating the domains without waxpresent is a valid approximation to the phases or domains in theformulations where wax is present.

The adhesive or article comprising a layer of adhesive material maycomprise any combination of the above parameters. In some embodiments,the adhesive or adhesive material may be derived from, comprise, or beselected from catalytically polymerized tackifiers, thermallypolymerized tackifiers, natural resin tackifiers, rosin tackifiers,non-hydrogenated tackifiers, non-thermally polymerized tackifiers,and/or non-aromatic tackifiers and/or combinations thereof. Otherembodiments may comprise one or more tackifiers as described below.Still other embodiments may comprise wax-free adhesive compositions, orcompositions with less than about 20 wt % wax, more preferably less thanabout 15 wt % wax, more preferably less than about 10 wt % wax, and morepreferably less than about 5 wt % wax based on the total weight of theadhesive composition.

Applicants believe that by using specific tackifiers in adhesivecompositions, the average stiffness domain area, the average pull-offforce domain area, the stiffness domain distribution and the pull-offforce domain distribution can be controlled to yield high performingadhesive materials. It is also believed that in adhesive compositionscomprising wax, the wax crystal size and wax crystal distribution can becontrolled to yield improved adhesive materials.

If no tackifier is used, the adhesive matrix may still comprise domainsas described herein, and the same principles would apply to suchformulations.

Adhesive Formulations

Typical adhesive formulations generally comprise one or more tackifiersand one or more polyolefins. For example, typical hot melt adhesivescomprise about 10–40 wt % adhesive polymer such as an SIS or SBS blockcopolymer, about 50–70 wt % tackifier and about 5–30 wt % oil or otheradditives described herein. Typical packaging or bookbinding hot meltadhesives comprise about 20–55 wt % adhesive polymer such as an EVAcopolymer, about 35–60 wt % tackifier and about 5–30 wt % oil, wax orother additives described herein. Typical pressure sensitive adhesivescomprise about 25–50 wt % adhesive polymer, such as a SIS blockcopolymer, about 40–70 wt % tackifier and about 0–20 wt % oil or othersuitable additive. These weight percents are based on the total weightof the adhesive formulation.

Tackifiers

The tackifier is preferably selected from the group consisting of:aliphatic hydrocarbon resins, hydrogenated aliphatic hydrocarbon resins,aromatic hydrocarbon resins, hydrogenated aromatic resins,aliphatic/aromatic hydrocarbon resins, hydrogenated aliphatic/aromatichydrocarbon resins, cycloaliphatic hydrocarbon resins, hydrogenatedcycloaliphatic resins, cycloaliphatic/aromatic hydrocarbon resins,hydrogenated cycloaliphatic/aromatic hydrocarbon resins, polyterpeneresins, terpene-phenol resins, rosin esters, grafted versions of any ofthe above, and mixtures of any two or more thereof. As used herein, theterm tackifier includes, but is not limited to, hydrocarbon resins,oligomers and/or resin material and the terms may be usedinterchangeably. Preferred tackifiers have a Mw less than about 10,000.

The tackifiers may have a softening point between about 80–180° C. Ifaromatics are present, the tackifier preferably has an aromatic contentof about 1–60%, more preferably about 1–40%, more preferably about1–20%, more preferably about 1–15%, more preferably about 5–15%, morepreferably about 10–20%, more preferably about 15–20%, and in anotherembodiment, more preferably about 1–10%, and more preferably-about5–10%, wherein any upper limit and any lower limit of aromatic contentmay be combined for a preferred range of aromatic content. The tackifiermay or may not be hydrogenated, either partially or substantially asdefined below.

Hydrocarbon Resin Production

Hydrocarbon resins are well known and are produced, for example, byFriedel-Crafts polymerization of various feeds, which may be puremonomer feeds or refinery streams containing mixtures of variousunsaturated materials. Generally speaking, the purer the feed the easierto polymerize. For example pure styrene, pure a-methyl styrene andmixtures thereof are easier to polymerize than a C₈/C₉ refinery stream.Similarly, pure or concentrated piperylene is easier to polymerize thanC₄–C₆ refinery streams. These pure monomers are, however, more expensiveto produce than the refinery streams which are often by-products oflarge volume refinery processes.

Aliphatic hydrocarbon resins can be prepared by cationic polymerizationof a cracked petroleum feed containing C₄, C₅, and C₆ paraffins,olefins, and conjugated diolefins referred to herein as C₅ monomers. Asused herein, C₅ monomers preferably excludes dicyclopentadiene (DCPD)monomer removed by thermal soaking as described below. These monomerstreams comprise cationically and thermally polymerizable monomers suchas butadiene, isobutylene, 1,3-pentadiene (piperylene) along with1,4-pentadiene, cyclopentene, 1-pentene, 2-pentene, 2-methyl-1-pentene,2-methyl-2-butene, 2-methyl-2-pentene, isoprene, cylcohexene,1-3-hexadiene, 1-4-hexadiene, cyclopentadiene, and dicyclopentadiene. Toobtain these C₅ monomer feeds the refinery streams are preferablypurified usually by both fractionation and treatment to removeimpurities. In some embodiments, the C₅ monomer feed stream may includeat least some cyclopentadiene (CPD) and substituted cyclopentadiene(e.g., methylcyclopentadiene) components. These components areoptionally separated from the C₅ monomer streams by thermal soakingwherein the C₅ monomer feed stream is heated to a temperature between100° C. and 150° C. for 0.5 to 6 hours followed by separation of theDCPD monomers, to reduce the level of cyclopentadiene ordicyclopentadiene in the C₅ monomer stream to preferably below 2 wt %.Low temperature heat soaking is preferred in order to limit the cyclicdiene (cyclopentadiene and methylcyclopentadiene) co-dimerization withC₅ linear conjugated dienes (isoprene and pentadienes 1,3 cis- andtrans-). The thermal soaking step preferably dimerizes thecyclopentadiene and substituted cyclopentadiene, making separation fromthe C₅ monomer stream easier. After fractionation and, if carried out,thermal soaking, the feedstock is preferably subjected to distillationto remove cyclic conjugated diolefins which are gel precursors(cyclopentadiene and methylcyclopentadiene being removed as dimers,trimers, etc.).

One example of a C₅ monomer stream is a steam cracked petroleum streamboiling in the range of −10° C. to 100° C. Examples of commercialsamples of C₅ monomer feedstocks include Naphtha Petroleum 3 Piperylenesfrom Lyondell Petrochemical Company, Houston, Tex., and regularPiperylene Concentrate or Super Piperylene Concentrate both from ShellNederland Chemie B. V., Hoogvliet, the Netherlands.

The resin polymerization feed may also comprise C₈–C₁₀ aromatic monomers(referred to herein as C₉ monomers) such as styrene, indene, derivativesof styrene, derivatives of indene, and combinations thereof.Particularly preferred aromatic olefins include styrene,α-methylstyrene, β-methylstyrene, indene, methylindenes and vinyltoluenes. One example of a C₉ monomer stream is a steam crackedpetroleum stream boiling in the range of −10° C. to 210° C. (135° C. to210° C. if the C₅ monomers and DCPD components are not present).Examples of commercial C₉ monomer feedstocks include LRO-90 fromLyondell Petrochemical Company, Houston, Tex., DSM C₉ Resinfeed Classicfrom DSM, Geleen, the Netherlands, RO-60 and RO-80 from Dow ChemicalCompany of Midland, Mich., and Dow Resin Oil 60-L from the Dow ChemicalCompany of Terneuzen, the Netherlands.

In addition to the reactive components, non-polymerizable components inthe feed may include saturated hydrocarbons such as pentane,cyclopentane, or 2-methylpentane that can be co-distilled with theunsaturated components. This monomer feed can be co-polymerized withother C₄ or C₅ olefins or dimers. Preferably, however, the feeds arepurified to remove unsaturated materials that adversely affect thepolymerization reaction or cause undesirable colors in the final resin(e.g., isoprene). This is generally accomplished by fractionation. Inone embodiment, polymerization is conducted using Friedel-Craftspolymerization catalysts such as supported or unsupported Lewis acids(e.g., boron trifluoride (BF₃), complexes of boron trifluoride, aluminumtrichloride (AlCl₃), complexes of aluminum trichloride or alkyl aluminumhalides, particularly chlorides). Suitable reaction conditions forFriedel-Crafts polymerization include temperatures of −20° C. to 100°C., and pressures of 100 to 2000 kPa. C₅ and C₉ monomers may bepolymerized by such a process.

Typically, the feed stream includes from 20–80 wt % monomers and 20–80wt % solvent, based on the total weight of the feed stream. Preferably,the feed stream includes 30–70 wt % monomers and 30–70 wt % of solvent.More preferably, the feed stream includes 50–70 wt % monomers and 30–50wt % of solvent. The solvent may include an aromatic solvent, which maybe toluenes, xylenes, other aromatic solvents, aliphatic solvents and/ormixtures of two or more thereof. The solvent is preferably recycled. Thesolvent may comprise the unpolymerizable component of the feed. Thesolvents generally contain less than 250 ppm water, preferably less than100 ppm water, and most preferably less than 50 ppm water.

The monomers in the feed stream may include 30–95 wt % of C₅ monomers,as described above and 5–70 wt % of a co-feed including at least onemember selected from the group consisting of pure monomer, C₉ monomers,and terpenes. Preferably, the feed stream includes about 50–85 wt % ofC₅ monomers and about 15–50 wt % of a co-feed, including at least onemember selected from the group consisting of pure monomer, C₉ monomers,and terpenes. The weight percents in this paragraph are based on thetotal weight of the feed monomers.

Typically, the resulting hydrocarbon resin has a number averagemolecular weight (Mn) of 400–3000, a weight average molecular weight(Mw) of 500–6000, a z-average molecular weight (Mz) of 700–15,000 and apolydispersity (PD) as measured by Mw/Mn of from 1.5 to 4.

The monomer feed can be copolymerized with C₄ or C₅ olefins or theirolefinic dimers as chain transfer agents. Up to 40 wt %, preferably upto 20 wt % based on the total weight of the feed, of chain transferagents may be added to obtain resins with lower and narrower molecularweight distributions than can be prepared from using the monomer feedalone. Components which behave as chain transfer agents in thesereactions include, but are not limited to, 2-methyl-1-butene,2-methyl-2-butene or dimers or oligomers of these species. The chaintransfer agent can be added to the reaction in pure form or diluted in asolvent.

A DCPD resin and/or oligomers thereof (referred to also as CPDoligomers) may be obtained by thermal polymerization of a feedcomprising unsaturated monomers of DCPD and/or substituted DCPD. Thefeed may also comprise aromatic monomers as previously described.Generally, a mixture of (a) DCPD stream, preferably a steam crackedpetroleum distillate boiling in the range 80–200° C., more preferably140° C. to 200° C., containing dimers and codimers of cyclopentadieneand its methyl derivatives together with (b) C₉ monomers, preferably asteam cracked distillate boiling in the range 150–200° C. comprisingα-methyl styrene, vinyl toluenes, indene and methyl indene with other C₉and C₁₀ aromatics, in the weight ratio (a:b) of from 90:10 to 50:50 isheated in a batch polymerization reactor to 160–320° C. at a pressure of980 kPa to 2000 kPa (more preferably 9.8×10⁵−11.7×10⁵ Pa), for 1.2 to 4hours, more preferably 1.5 to 4 hr. Where inclusion of the oligomers isnot desired, the resulting polymerizate may be steam stripped to removeinert, unreacted, and low molecular weight oligomeric components toyield a resin having a softening point in the range of 80–120° C.

The resin may also be obtained by or derived from thermal polymerizationof a feed comprising C₅ monomers and C₉ monomers as previouslydescribed. In such embodiments, a mixture of (a) C₅ monomers,preferably, a steam cracked petroleum distillate boiling in the range80–200° C. containing C₅ monomers together with (b) C₉ monomers,preferably a steam cracked distillate boiling in the range 150–200° C.comprising α-methyl styrene, vinyl toluenes, indene and methyl indenewith other C₈–C₁₀ aromatics, in the weight ratio (a:b) of from 90:10 to50:50 is heated in a batch polymerization reactor to 160–320° C. at apressure of 980 kPa to 2000 kPa (more preferably 9.8×10⁵−11.7×10⁵ Pa),for 1.2 to 4 hours, more preferably 1.5 to 4 hr. Where inclusion of theoligomers is not desired, the resulting polymerizate may be steamstripped to remove inert, unreacted, and low molecular weight oligomericcomponents to yield a resin having a softening point in the range of80–120° C.

The products of the polymerization process include both resin and anoligomer by-product comprising oligomers (dimers, trimers, tetramers,pentamers, and hexamers, and optionally septamers and octamers) of thefeed monomer(s). As used hereafter, resin material refers to the resin,the oligomers, or a mixture of the two. Where the oligomer by-productresults from thermal polymerization of DCPD and substituted DCPD, theoligomers are typically a complex mixture of (preferably hydrogenated asdescribed below) Diels Alder trimers and tetramers of CPD and methyl-CPDwith low levels of acyclic C₅ diolefins such as 1,3-pentadiene andisoprene.

The resin material is then preferably hydrogenated to reduce colorationand improve color stability. Any of the known processes forcatalytically hydrogenating resin material can be used. In particular,the processes disclosed in U.S. Pat. Nos. 5,171,793, 4,629,766,5,502,104 and 4,328,090, and in WO 95/12623 are suitable. Generichydrogenation treating conditions include reactions in the temperaturerange of about 100–350° C. and pressures of from 5 atm (506 kPa) to 300atm (30390 kPa) hydrogen (and even up to 400 atm hydrogen), for example,10–275 atm (1013–27579 kPa). In one embodiment the temperature is in therange of from 180–330° C. and the pressure is in the range of from15195–20260 kPa hydrogen. The hydrogen to feed volume ratio to thereactor under standard conditions (25° C., 1 atm (101 kPa) pressure)typically can range from 20:1–200:1; for water-white resins 100:1–200:1is preferred. The hydrogenated product may be stripped to remove lowmolecular weight by-products and any solvent. This oligomeric by-productis a low-viscosity nearly colorless liquid boiling between 250–400° C.and is preferably substantially hydrogenated.

The hydrogenation of the resin material may be carried out via molten orsolution based processes by either a batch or, more commonly, acontinuous process. Catalysts used for the hydrogenation of hydrocarbonresins are typically supported monometallic and bimetallic catalystsystems based on group 6, 8, 9, 10 or 11 elements. Catalysts such asnickel on a support (for example, nickel on alumina, nickel on charcoal,nickel on silica, nickel on kieselguhr, etc.), palladium on a support(for example, palladium on silica, palladium on charcoal, palladium onmagnesium oxide, etc.) and copper and/or zinc on a support (for examplecopper chromite on copper and/or manganese oxide, copper and zinc onalumina, etc.) are good hydrogenation catalysts. The support materialtypically comprises such porous inorganic refractory oxides as silica,magnesia, silica-magnesia, zirconia, silica-zirconia, titania,silica-titania, alumina, silica-alumina, alumina-silicate, etc., withsupports containing γ-alumina being highly preferred. Preferably, thesupports are essentially free of crystalline molecular sieve materials.Mixtures of the foregoing oxides are also contemplated, especially whenprepared as homogeneously as possible. Useful support materials includethose disclosed in U.S. Pat. Nos. 4,686,030, 4,846,961, 4,500,424, and4,849,093. Suitable supports include alumina, silica, carbon, MgO, TiO₂,ZrO₂, Fe₂O₃ or mixtures thereof.

Another suitable process for hydrogenating the resin material isdescribed in EP 0082726. EP 0082726 describes a process for catalytic orthermal hydrogenation using a nickel-tungsten catalyst on agamma-alumina support, wherein the hydrogen pressure is1.47×10⁷−1.96×10⁷ Pa and the temperature is in the range of 250–330° C.After hydrogenation the reactor mixture may be flashed and furtherseparated to recover hydrogenated resin material. In one embodiment,steam distillation may be used to separate the oligomers and ispreferably conducted without exceeding 325° C. resin temperature.

The catalyst may comprise nickel and/or cobalt with one or more ofmolybdenum and/or tungsten on one or more of alumina or silica supports,wherein the amount of nickel oxide and/or cobalt oxide on the supportranges from 2–10 wt %, based on the total weight of the catalyst. Theamount of tungsten or molybdenum oxide on the support after preparationranges from 5–25 wt %, based on the total weight of the catalyst.Preferably, the catalyst contains 4–7 wt % nickel oxide and 18–22 wt %tungsten oxide. This process and suitable catalysts are described ingreater detail in U.S. Pat. No. 5,820,749. In another embodiment, thehydrogenation may be carried out using the process and catalystsdescribed in U.S. Pat. No. 4,629,766. In particular, nickel-tungstencatalysts on gamma-alumina are preferred.

The oligomers may be stripped from the resin before hydrogenation andare preferably hydrogenated before grafting (if necessary and asdescribed below). The oligomers may also be hydrogenated with the resinand then stripped from the resin, yielding a hydrogenated resin andhydrogenated oligomers. At least some of the oligomers may be strippedbefore hydrogenation and at least some hydrogenated oligomers may bestripped after hydrogenation. The hydrogenated resin/oligomers productmay be grafted as described below. The oligomers may also be derivedfrom any suitable source and hydrogenated (if necessary) before graftingso that the oligomers before grafting are typically at least partiallyhydrogenated and preferably substantially hydrogenated.

Grafted Tackifiers and Tackifier Components

As used herein, a grafted tackifier, or grafted hydrocarbon resin,oligomer, and/or resin material, or a combination thereof means it hasbeen combined, contacted, and/or reacted with a graft monomer. Graftingis the process of combining, contacting, or reacting the hydrocarbonresin, oligomers and/or resin material with the graft monomer. Graftinghydrocarbon resins, oligomers, and/or resin material, or a combinationthereof to include at least some polar functionality produces usefultackifier component for many applications.

Grafted resin materials may include, but are not limited to: adhesivesor adhesive components comprising (i) grafted hydrocarbon resins; (ii)grafted oligomers, (iii) grafted oligomers+ungrafted resin(s), (iv)grafted hydrocarbon resin+ungrafted resin(s), (v) grafted hydrocarbonresin+ungrafted oligomers, (vi) grafted hydrocarbon resin+graftedoligomers, (vii) grafted oligomers+ungrafted oligomers or (viii) graftedhydrocarbon resin+grafted oligomers+ungrafted resin(s) and othersuitable combinations of one or more thereof.

Suitable hydrocarbon resins that may be grafted include: aliphatichydrocarbon resins, at least partially hydrogenated aliphatichydrocarbon resins, aliphatic/aromatic hydrocarbon resins, at leastpartially hydrogenated aliphatic aromatic hydrocarbon resins,cycloaliphatic hydrocarbon resins, at least partially hydrogenatedcycloaliphatic resins, cycloaliphatic/aromatic hydrocarbon resins, atleast partially hydrogenated cycloaliphatic/aromatic hydrocarbon resins,at least partially hydrogenated aromatic hydrocarbon resins, polyterpeneresins, terpenephenol resins, and mixtures of two or more thereof.

The resin and/or oligomers are preferably at least partiallyhydrogenated and more preferably substantially hydrogenated. As usedherein at least partially hydrogenated means that the material containsless than about 90% olefinic protons, more preferably less than about75% olefinic protons, more preferably less than about 50% olefinicprotons, more preferably less than about 40% olefinic protons, morepreferably less than about 25% olefinic protons, more preferably lessthan about 15% olefinic protons, more preferably less than about 10%olefinic protons, more preferably less than about 9% olefinic protons,more preferably less than about 8% olefinic protons, more preferablyless than about 7% olefinic protons, and more preferably less than about6% olefinic protons. As used herein, substantially hydrogenated meansthat the material contains less than about 5% olefinic protons, morepreferably less than about 4% olefinic protons, more preferably lessthan about 3% olefinic protons, more preferably less than about 2%olefinic protons, more preferably less than about 1% olefinic protons,more preferably less than about 0.5% olefinic protons, more preferablyless than about 0.1% olefinic protons, and more preferably less thanabout 0.05% olefinic protons after hydrogenation (and before reactionwith the graft monomer). The degree of hydrogenation is typicallyconducted so as to minimize and preferably avoid hydrogenation of thearomatic bonds. In preferred embodiments wherein the resin and/oroligomers are substantially hydrogenated, it is believed that the graftmonomer is appended to the resin/oligomer backbone as opposed to forminga copolymer (of resin/oligomers and graft monomers) because of the lackof terminal olefinic bonds on the substantially hydrogenatedresin/oligomers (as indicated by the preferred low olefinic protonmeasurements).

The hydrocarbon resin/and or oligomers have an aromatic content of about1–60%, more preferably about 1–40%, more preferably about 1–20%, morepreferably about 1–15%, more preferably about 5–15%, more preferablyabout 10–20%, more preferably about 15–20%, and in another embodiment,more preferably about 1–10%, and more preferably about 5–10%, whereinany upper limit and any lower limit of aromatic content may be combinedfor a preferred range of aromatic content. In one embodiment, thehydrocarbon resin to be grafted has a softening point of about 10–200°C., more preferably about 10–160° C., more preferably about 60–130° C.,more preferably about 90–130° C., more preferably about 80–120° C., morepreferably about 80–150° C., and more preferably about 90–110° C.,wherein any upper limit and any lower limit of softening point may becombined for a preferred softening point range. Softening point (° C.)is preferably measured as a ring and ball softening point according toASTM E-28 (Revision 1996).

Suitable grafted resins include EMFR 100, 100A, and 101 available fromExxonMobil Chemical Company. In one embodiment, a grafted resincomprises hydrocarbon resins produced by the thermal polymerization ofdicyclopentadiene (DCPD) or substituted DCPD which are then grafted witha graft monomer. The resin may further include aliphatic or aromaticmonomers as described later. In another embodiment, the hydrocarbonresin is produced by the thermal polymerization of dicyclopentadiene(DCPD) or substituted DCPD and C₉ monomers or thermal or catalyticpolymerization of C₅ and C₉ monomers. In a preferred embodiment, thegrafted resins contain less than 10% aromatics in the final resinproduct. In another embodiment, the grafted resin comprises 95 wt % of athermally polymerized dicyclopentadiene resin comprising about 10%aromatics, available as Escorez™ 5600, grafted with maleic anhydride,and 5 wt % of grafted oligomers derived from the production of Escorez™5600 and also grafted with maleic anhydride.

Grafted Oligomers

The hydrocarbon resin may also comprise oligomers (dimers, trimers,tetramers, pentamers, hexamers and optionally septamers and octamers),preferably derived from a petroleum distillate boiling in the range of30–210° C. The oligomers can be derived from any suitable process andare often derived as a byproduct of resin polymerization, whetherthermal or catalytic. The oligomers may be derived from processeswherein suitable DCPD, C₅ and/or C₉ monomer feeds (as described below)are oligomerized and then grafted. Suitable oligomer streams havemolecular weights (Mn) of from about 130–500, more preferably from about130–410, more preferably from about 130–350, more preferably from about130–270, more preferably from about 200–350, and more preferably fromabout 200–320. The oligomers may be grafted as described herein.

The oligomers may comprise cyclopentadiene and substitutedcyclopentadiene monomers and may further comprise C₉ monomers. Inanother embodiment, the oligomers comprise C₅ monomers and may furthercomprise C₉ monomers. Other monomers may also be present, includingC₄–C₆ mono- and di-olefins and terpenes. The oligomers may also besolely C₉ monomers. Specific examples of suitable individualcyclopentadiene and substituted cyclopentadiene monomers (includingDCPD), C₉ monomers and C₅ monomers are described herein. Suitableoligomers may also comprise a mixture of more or more preferred oligomermaterials as described herein.

Graft Monomers

Preferred graft monomers include any unsaturated organic compoundcontaining at least one olefinic bond and at least one polar group suchas a carbonyl group, which includes unsaturated acids and anhydrides andderivatives thereof. Preferably, the organic compound contains anethylenic unsaturation conjugated with a carbonyl group (—C═O) andpreferably contains at least one α, β olefin bond. Examples includecarboxylic acids, acid halides or anhydrides, phenols, alcohols(mono-alcohols, diols, and polyols), ethers, ketones, alkyl and aromaticamines (including polyamines), nitriles, imines, isocyanates, nitrogencompounds, halides and combinations and derivatives thereof.Representative acids and acid derivatives include carboxylic acids,anhydrides, acid halides, esters, amides, imides and their salts, bothmetallic and non-metallic. Examples include maleic, fumaric, acrylic,methacrylic, itaconic, aconitic, citraconic, himic, tetrahydrophthalic,crotonic, α-methyl crotonic, and cinnamic acids. Maleic anhydride is aparticularly preferred graft monomer. Particular examples include,itaconic anhydride, citraconic anhydride, methyl acrylate, methylmethacrylate, ethyl acrylate, ethyl methacrylate, glycidyl acrylate,monoethyl maleate, diethyl maleate, dibutyl maleate, monomethylfumarate, dimethyl fumarate, monomethyl itaconate, diethyl itaconate,acrylamide, methacrylamide, maleic acid monoamide, maleic acid diamide,maleic acid-N-monoethylamide, maleic acid-N,N-diethylamide, maleicacid-N-monobutylamide, maleic acid-N,N-dibutylamide, fumaric acidmonoamide, fumaric acid diamide, fumaric acid-N-monobutylamide, fumaricacid-N,N-dibutylamide, maleimide, N-butylmaleimide, N-phenylmaleimide,sodium acrylate, sodium methacrylate, potassium acrylate and potassiummethacrylate. Preferred graft monomers include acids, anhydrides,alcohols, amides, and imides.

Grafting the Resin Material

At least a portion of the resulting resin material, preferably derivedfrom a process such as that described above, may then be combined and/orcontacted with a graft monomer, typically under suitable reactionconditions and in a suitable mixing device. The reaction is preferablyconducted in the absence of significant shear. As previously described,the resin and oligomers may be grafted separately or simultaneously, andif separately, grafted oligomers may then be optionally remixed with thegrafted resin, an ungrafted resin, or any another suitable resin,adhesive component or composition as described below.

Grafting of the graft monomer preferably occurs in the presence of afree-radical initiator selected from the group consisting of organicperoxides, organic per-esters, and azo compounds. Examples of suchcompounds include benzoyl peroxide, dichlorobenzoyl peroxide, dicumylperoxide, di-tert-butyl peroxide,2,5-dimethyl-2,5-di(peroxybenzoate)hexyne-3,1,4-bis(tert-butylperoxyisopropyl)benzene,lauroyl peroxide, tert-butyl peracetate,2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3,2,5-dimethyl-2,5-di(tert-butylperoxy)hexane,tert-butyl perbenzoate, tert-butylperphenyl acetate, tert-butylperisobutyrate, tert-butyl per-sec-octoate, tert-butyl perpivalate,cumyl perpivalate, tert-butyl hydroperoxide, tert-butylperdiethylacetate, azoisobutyronitrile, and dimethyl azoisobutyrate. Theperoxide preferably has a half-life of about 6 minutes at 160° C. withvolatile non-aromatic decomposition products and those that minimizecolor formation. Preferred peroxides include di-tert-butyl peroxide and2,5 dimethyl-2,3-di(tert-butylperoxy)hexane. The amount of peroxidecombined is typically dependent on the weight of the graft monomer. Theweight ratio of the graft monomer:peroxide in the reaction mixture maybe from 1 to 20, more preferably from about 1 to 10, more preferablyfrom about 1 to about 5, and even more preferably about 4.

The graft monomers may be combined with the resin material at atemperature of from 50–200° C., more preferably from 70–150° C., morepreferably from 70–125° C., more preferably from 140–180° C., morepreferably from 140–180° C., more preferably from 155–165° C. or from165–175° C., and a pressure of typically one atmosphere but higherpressures can be used if necessary. In another preferred embodiment, thegrafting reaction occurs at temperature greater than 90° C., morepreferably from 90° C. to any temperature limit described above, morepreferably from 90° C. to 150° C., more preferably from 90° C. to 145°C. In general, the lower limit of the reaction temperature is governedby the softening point of the resin as it is preferred to conduct thegrafting reactions at temperatures above the softening point of thematerial to be grafted.

The graft monomer may be combined so that the weight ratio of graftmonomer:resin material in the reaction mixture is less than 1, morepreferably less than 0.5 more preferably less than 3:10 and morepreferably less than 3:20. In a preferred embodiment, the reactionmixture is maintained in a homogenous state. The reaction mixture ispreferably agitated or stirred vigorously. The free radical initiator iscombined with the resin material-graft monomer reaction mixture eitherin one addition or preferably in a continuous or semi-continuous modeduring the reaction. Residence time in the reaction zone is preferablyless than 75 minutes, more preferably less than 60 minutes, morepreferably from 10–60 minutes, even more preferably from 30–60 minutes.

Where only the oligomers are grafted, the reaction temperature ispreferably from 50–200° C., more preferably from 70–150° C., morepreferably from 70–125° C., more preferably from 140–180° C., morepreferably from 140–180° C., more preferably from 155–165° C., and morepreferably about 160° C. In another embodiment the reaction temperatureis 170–185° C. In another preferred embodiment, the grafting reactionoccurs at temperature greater than 90° C., more preferably from 90° C.to any temperature limit described above, more preferably from 90° C. to150° C., more preferably from 90° C. to 145° C. Other preferred rangesmay include ranges from any lower to any upper temperature described inthis paragraph.

The amount of graft monomer added is typically dependent on the amountof oligomer. Preferably, the oligomer:graft monomer mole ratio is from 5to 0.2, more preferably from 2 to 0.5, more preferably from about 1.5 to0.67 and more preferably about 1. Thereafter, the ungrafted oligomersare stripped from the product and optionally recycled to the reactionzone. The grafted oligomers produced generally have a softening point offrom 0–120° C., more preferably from 25–120° C., more preferably from50–120° C. and even more preferably from 80–110° C., and color of 4–10Gardner. Gardner color, as used herein, is measured using ASTM D-6166.The grafted oligomer product can then be recombined with the resin(grafted or ungrafted) from which it was derived or combined with otherresins, polymers, and/or other materials and formulated into andadhesive material.

Where only the resin is grafted, the reaction temperature is preferablybetween 50–200° C., more preferably between 70–150° C., more preferablybetween 70–125° C., more preferably between 140–180° C., more preferablybetween 140–180° C., more preferably between 165–175° C., and morepreferably about 170° C. In another embodiment, the grafting reactionpreferably occurs between 170–185° C. In another preferred embodiment,the grafting reaction occurs at temperature greater than 90° C., morepreferably between 90° C. and any upper temperature limit describedabove. The amount of graft monomer added is typically dependent on theamount of resin. The graft monomer:resin weight ratio in the reactionmixture is preferably less than 1:5, more preferably less than 1:10,more preferably less than 1:20, and even more preferably about 1:40.Generally, the grafting raises the softening point of the resin lessthan 10° C., more preferably less than 5° C. and produces a graftedresin having a color between 1–6 Gardner.

In another embodiment, the oligomers are not stripped from the resinproduct, and the resin and oligomers are simultaneously grafted.Reaction conditions are similar to those previously described forgrafting the resin, but the graft monomer:resin material weight ratio isgenerally kept below 0.5, more preferably below 0.25 and more preferablybelow 3:20. Upon completion of grafting, the material may be furtherstripped if required to yield a resin of the desired softening pointand/or to remove unreacted oligomers. Separation of the graftedoligomers from the grafted resin may also be made if desired, but theproduct may be used without such further processing. In many embodimentscomprising grafted resin and grafted oligomers, the weight ratio ofgrafted oligomers:grafted resin in the resin material will be greaterthan 0.005, more preferably greater than 0.01, more preferably greaterthan 0.02, more preferably greater than 0.05, and more preferablygreater than 0.1.

Grafting of the resin material can also be conducted via a solutionroute wherein the resin material dispersed in a solvent and combined,contacted and/or reacted with the graft monomer. Additionally oralternatively, the graft monomer can be dispersed in a solvent prior toadding to the resin material. These routes allow for lower reactiontemperatures (as low as 80° C. or 100° C.) and allows the choice ofdifferent peroxides having half-lives of 6 minutes at the lower reactiontemperatures. Suitable solvents include, but are not limited to,aliphatic solvents, cycloaliphatic solvents, aromatic solvents, andaromatic-aliphatic solvents. Typical examples include benzene, toluene,xylene, chlorobenzene, n-pentane, n-hexane, n-heptane, n-octane,n-decane, iso-heptane, iso-decane, iso-octane, cyclohexane, alkylcyclohexane, and combinations of two or more thereof.

The resulting grafted resin material preferably has a softening pointbetween about 15–210° C., more preferably about 15–170° C., morepreferably about 65–140° C., more preferably about 65–130° C., morepreferably about 80–120° C., more preferably about 90–110° C., and morepreferably between about 85–110° C. The grafted resin materialpreferably has a glass transition temperature (Tg) less than about 120°C., more preferably less than about 110° C., more preferably from about25–100° C., more preferably from about 60–100° C., more preferably about60–80° C., and more preferably from about 35–70° C. In one embodimentthe Tg is preferably less than 50° C. Differential Scanning Calorimetry(DSC, ASTM D 341-88) was used to measure Tg. The resulting grafted resinmaterial preferably has a Saponification number (mg KOH/g resinmaterial) greater than about 10, more preferably greater than about 12,more preferably greater than about 15, more preferably greater thanabout 16, more preferably greater than about 17, more preferably greaterthan about 18, more preferably greater than about 19, more preferablygreater than about 20, more preferably greater than about 25. Theresulting grafted resin material preferably has an acid number greaterthan about 10, more preferably greater than about 15, more preferablygreater than about 16, more preferably greater than about 17, morepreferably greater than about 18, more preferably greater than about 19,more preferably greater than about 20, and more preferably greater thanabout 25.

In one embodiment, the grafted resin material has a resin material:graftmonomer molar ratio of from about 50–0.5, more preferably from about10–2, more preferably from about 5–2, more preferably from about1.5–0.67, and more preferably about 1. In some embodiments, the weightratio of graft monomer:resin in a grafted resin product is preferablyless than about 1, in other embodiments from about 0.001–1, in otherembodiments from about 0.01–1, in other embodiments from about 0.02–1,in other embodiments from about 0.1–1, in other embodiments from about0.33–1, and in other embodiments from about 0.01–0.3, and in otherembodiments from about 0.1–0.2. The grafted resin material preferablycontains less than about 10 wt % graft monomer, more preferably lessthan about 5 wt % graft monomer, more preferably less than about 3 wt %graft monomer and even more preferably from about 2–3 wt % graftmonomer.

Resin Blends

Resin blends may also be used. The blends comprising the grafted resinmaterial described herein include both: (i) partially grafted resinmaterial streams wherein only a portion of the resin material in aparticular stream is grafted (resulting in a mixture of grafted andun-grafted resin material); and, (ii) blends of partially or fullygrafted resin material streams with another tackifying resin. Suitableexamples of other tackifying resins include: aliphatic hydrocarbonresins, at least partially hydrogenated aliphatic hydrocarbon resins,aliphatic/aromatic hydrocarbon resins, at least partially hydrogenatedaliphatic aromatic hydrocarbon resins, cycloaliphatic hydrocarbonresins, at least partially hydrogenated cycloaliphatic resins,cycloaliphatic/aromatic hydrocarbon resins, at least partiallyhydrogenated cycloaliphatic/aromatic hydrocarbon resins, aromatichydrocarbon resins, at least partially hydrogenated aromatic hydrocarbonresins, polyterpene resins, terpene-phenol resins, rosin esters, rosinacids, resins grafted with graft monomers, and mixtures of any two ormore thereof. Suitable resins also include other resins having polarfunctionality whether produced by processes described herein or othersuitable processes.

For example, one embodiment is a composition comprising from about0.1–99 wt % grafted resin material and from about 1–99.9 wt % otherresin, based on the total weight of the composition. Other embodimentscomprise from about 0.1–50 wt % grafted resin material, from about0.1–30 wt % grafted resin material, from about 0.1–20 wt % grafted resinmaterial, from about 1–25 wt % grafted resin material, from, about 1–15wt % grafted. resin material, from, about 1–10 wt % grafted resinmaterial, from about 5–10 wt % grafted resin material, and from about10–30 wt % grafted material, based on the total weight of thecomposition.

In a preferred embodiment, the resin material comprises grafted resinand grafted oligomers in amounts of from about 0.1–50 wt % graftedoligomers, more preferably from about 0.1–30 wt % grafted oligomers,more preferably from about 0.1–20 wt % grafted oligomer, more preferablyfrom about 0.1–10 wt % grafted oligomers, more preferably from about1–30 wt % grafted oligomers, more preferably from about 1–20 wt %grafted oligomers, and more preferably from about 1–10 wt % graftedoligomers based on the total weight of the resin material. Preferredranges also include between any upper and lower limit described in thisparagraph.

One blend is a composition comprising at least two hydrocarbon resins,wherein at least one of the resins is a grafted resin material graftedwith a graft monomer and the other resin is an ungrafted petroleumhydrocarbon resin. “At least two hydrocarbon resins” also includesembodiments of hydrocarbon resins wherein only a portion of the overallresin molecules have been grafted with a graft monomer. While the baseresin component may be the same, there are two resins—one grafted andone un-grafted resin within the resin composition. Such an embodimentmay include at least two hydrocarbon resins wherein the base resincomponents are different, e.g. a C₅/C₉ resin and a grafted CPD/C₉ resin.Other examples include any combination of ungrafted resins and graftedresin materials described herein. For example, suitable petroleumhydrocarbon resins include: aliphatic hydrocarbon resins, at leastpartially hydrogenated aliphatic hydrocarbon resins, aliphatic/aromatichydrocarbon resins, at least partially hydrogenated aliphatic aromatichydrocarbon resins, cycloaliphatic hydrocarbon resins, at leastpartially hydrogenated cycloaliphatic resins, cycloaliphatic/aromatichydrocarbon resins, at least partially hydrogenatedcycloaliphatic/aromatic hydrocarbon resins, aromatic hydrocarbon resins,at least partially hydrogenated aromatic hydrocarbon resins, polyterpeneresins, rosin esters, and terpene-phenol resins.

Polyolefins

Preferred polyolefins as described herein preferably have an Mw greaterthan 20,000.

Polyolefins suitable for use in adhesives as described herein includepolar polymers. As used herein, polar polymers include homopolymers,copolymers, and terpolymers containing polar groups such as esters,ethers, ketones, amides, imides, alcohols, phenols, halides, acids,anhydrides, sulfides, nitriles, isocyanates, aromatic and heteroaromaticgroups. These polar substituents may be found in the polymer backbone,pendant to the polymer backbone or attached to an aromatic group thatmay be either incorporated in the polymer backbone or pendant to thepolymer backbone. Suitable examples include copolymers of a C₂ to C₂₀olefin, such as ethylene and/or propylene and/or butene with one or morepolar monomers such as vinyl esters or alcohols, acids, anhydrides,acrylic or methacrylic acids or esters. Polar polymers also include anythermoplastic copolymer comprising a functional group capable ofinteracting with the unsaturated acid or anhydride group present withthe resin material. Examples include, but are not limited to, polymers(or copolymers of) such as polyesters, polyamides, polyureas,polycarbonates, polyacrylonitriles, polyacrylates, polymethylacrylates,ethylene vinyl esters, halogenated polymers, polyvinyl chloride,polyethylene terephthalate, polybutylene terephthalate (PBT),polyacetal, acrylic or methacrylic acids, alkyl acrylates, ormethacrylates, ethylene methyl acrylate, ethylene butyl acrylate, andthe like. Accordingly, in one embodiment, the grafted resin material maybe formulated with a polar polymer, such as EVA. It may optionallycomprise other components such as one or more waxes or oils.

Other suitable polyolefins include polyethylene, ethylene copolymerizedwith one or more C₃ to C₂₀ linear, branched, or cyclic α-olefins,polypropylene, propylene copolymerized with one or more of ethyleneand/or C₄ to C₂₀ linear, branched, or cyclic α-olefins, polybutylene,polybutylene copolymerized with one or more of C₅ to C₂₀ linear,branched, or cyclic α-olefins, low density polyethylene (LDPE) (density0.915 to less than 0.935 g/cm³) linear low density polyethylene (LLPDE),ultra low density polyethylene (density 0.86 to less than 0.90 g/cm³),very low density polyethylene (density 0.90 to less than 0.915 g/cm³),medium density polyethylene (density 0.915 to less than 0.945 g/cm³),and high density polyethylene (HDPE) (density 0.945 to 0.98 g/cm³ ).Other hydrocarbon polymers (or copolymers of) include: polybutene-1,polyisobutylene, polybutene, polyisoprene, polybutadiene, butyl rubber,amorphous polypropylene, ethylene propylene diene monomer rubber,natural rubber, styrene butadiene rubber, copolymers and halogenatedcopolymers of isobutylene and para-alkylstyrene, elastomers such asethylene-propylene rubber (EPR), vulcanized EPR, EPDM, nylons,polycarbonates, PET resins, polymers of aromatic monomers such aspolystyrene, copolymers of isobutylene and para-alkyl styrene, highmolecular weight HDPE, low molecular weight HDPE, graft copolymersgenerally, polyacrylonitrile homopolymer or copolymers, thermoplasticpolyamides, polyacetal, polyvinylidine fluoride and other fluorinatedelastomers, polyethylene glycols, polyisobutylene, or blends thereofPreferred α-olefins include propylene, butene, pentene, hexene, heptene,octene, nonene, dodecene, cyclopentene,3,5,5-trimethylhexene-1,3-methylpentene-1,4-methyl pentene-1 andterpolymers of the above monomers. In another embodiment, the copolymercomprises a terpolymer of (i) ethylene and/or (ii) a C₃ to C₂₀comonomer, and (iii) a diene. Preferred dienes include butadiene,pentadiene, hexadiene, norbornene, ethylidene norbornene, vinylnorbornene, dicyclopentadiene, and substituted versions thereof. Thearchitecture of such polymers may be linear, substantially linear,short-chain branched, long-chain branched, star branched or any othercombination thereof. The branches or arms may be the same as the mainbackbone or different such as branch-block polymers or multi-armedstars.

Suitable polyolefins also include block copolymers of styrene and one ormore conjugated dienes such as SI (Styrene-Isoprene), SBS(Styrene-Butadiene-Styrene), SB (Styrene-Butadiene), and SIS(Styrene-Isoprene-Styrene). Styrene block copolymers comprisingtetrablock or pentablock copolymers selected from SISI, SISB, SBSB,SBSI, ISISI, ISISB, BSISB, ISBSI, BSBSB, and BSBSI are also suitable.The block copolymers may be completely or partially hydrogenated to givea resulting SEBS (Styrene-Ethylene-Butene-Styrene) polymer. Thearchitecture of the block copolymers includes linear, radial ormulti-arm star, or multi-branched and may include various combinationsof styrene, isoprene, or butadiene, which may or may not behydrogenated.

Other suitable polyolefins include grafted polymers or blends of graftedpolymers and/or non-grafted polymers. Examples of polymers and of suchblends include, but are not limited to, those described in U.S. Pat. No.5,936,058.

Other suitable polyolefins include elastomers, in particular, to formadhesive sealants. Preferred elastomers include natural rubber,polyisoprene, polybutadiene, copolymers of butadiene with styrene,copolymers of butadiene with acrylonitrile, butyl rubber,polychloroprene, ethylene/propylene rubber and elastomeric copolymers ofethylene, propylene and a non-conjugated diene, styrenic blockcopolymers such as block copolymers of styrene and or a-methyl styrenewith an alkadiene (such as isoprene or butadiene) in linear, radial,and/or tapered form.

In one embodiment, the polyolefin may be a polymer produced using ametallocene catalyst system. Typically, the metallocene homopolymers orcopolymers are produced using mono- or bis-cyclopentadienyl transitionmetal catalysts in combination with an activator of alumoxane and/or anon-coordinating anion in solution, slurry, high-pressure or gas phase.The catalyst system may be supported or unsupported and thecyclopentadienyl rings may be substituted or unsubstituted. Titanium,zirconium and hafnium are preferred transition metals. Several productsproduced with such catalyst/activator combinations are commerciallyavailable from ExxonMobil Chemical Company in Baytown, Tex. under thetradenames EXCEED™ and EXACT™ or from Dow Chemical Company under thetradenames ENGAGE™ and AFFINITY™. Suitable polyolefins also includeplastomers.

The metallocene produced copolymers described above preferably have apolydispersity less than 4 and a composition distribution breadth index(CDBI) of 50% or more, preferably above 60%, even more preferably above70%. In one embodiment, the CDBI is above 80%, even more preferablyabove 90%, even more preferably above 95%. In one embodiment, thepolyethylene copolymer has a CDBI of from 60–85%, even more preferablyfrom 65–85%.

Composition Distribution Breadth Index (CDBI) is a measure of thecomposition distribution of monomer within the polymer chains and ismeasured by the procedure described in PCT publication WO 93/03093,published Feb. 18, 1993 including that fractions having a weight averagemolecular weight (Mw) below 15000 are ignored when determining CDBI.

The adhesive may also comprise additives well known in the art such asprocessing oils, performance oils, anti-block, anti-static,antioxidants, cross-linking agents, silica, carbon black, talc,pigments, fillers, processing aids, UV stabilizers, neutralizers,lubricants, anti-slip agents, slip agents, surfactants and/or nucleatingagents. Examples of common additives include: antioxidants such asIrganox™ 1010, silicon dioxide, titanium dioxide, polydimethylsiloxane,talc, dyes, wax, calcium stearate, carbon black and glass beads. In HMAapplications, suitable synthetic waxes include paraffin andmicrocrystalline waxes having melting points within a range from about55° C. to about 130° C. and low molecular weight polyethylene andFischer-Tropsch waxes. The wax content is preferably from about 1 toabout 35 wt.% of the total blend composition. In PSA applications,suitable oils include FLEXON™ 876 or PRIMOL™ 352 available fromExxonMobil Chemical Company at concentrations less than 50%.

The adhesives may be formulated into pressure sensitive adhesives thatmay be applied to any conventional backing layer such as paper, foil,polymeric film, release liners, woven or non-woven backing material tomake for example, packaging tapes, masking tapes and labels.

One embodiment of a hot melt pressure sensitive comprises 100 parts byweight of a polyolefin, preferably a styrene block copolymer, 50–150 phr(parts per 100 parts by weight polyolefin) of a resin as describedherein, 0–50 phr of an extender oil, more preferably 10–50 phr, morepreferably 15–50 phr, more preferably 20–50 phr, more preferably 25–50phr, more preferably 30–50 phr, more preferably 35–50 phr, morepreferably 40–50 phr, more preferably 45–50 phr, and 0–5 phrantioxidant.

Optional components in hot melt adhesives are plasticizers or otheradditives such as oils, tackifiers, surfactants, fillers, colormasterbatches, and the like. Preferred plasticizers include mineraloils, polybutenes, phthalates, and the like. Particularly preferredplasticizers include phthalates such as diisodecyl phthalate (DIOP),diisononylphthalate (DINP), and dioctylphthalates (DOP). Particularlypreferred oils include aliphatic naphthenic oils.

Another optional component of a hot melt adhesive is a low molecularweight product such as wax, oil, or low Mn polymer (low meaning below Mnof 5000, preferably below 4000, more preferably below 3000, even morepreferably below 2500). Preferred oils include aliphatic naphthenicoils, white oils, or the like. Preferred low Mn polymers includepolymers of lower α-olefins such as propylene, butene, pentene, andhexene. A particularly preferred polymer includes polybutene having a Mnof less than 1000. An example of such a polymer is available under thetrade name PARAPOL™ 950 from ExxonMobil Chemical Company. PARAPOL™ 950is a liquid polybutene polymer having a Mn of 950 and a kinematicviscosity of 220 cSt at 100 ° C., as measured by ASTM D 445. Suitableembodiments of HMAs generally comprise 20–70 wt % resin material orblends as described herein, 30–80 wt % polyolefin, and 0–35 wt % wax.

HMA embodiments can be used for disposable diaper and napkin chassisconstruction, elastic attachment in disposable goods, converting,packaging, labeling, bookbinding, woodworking, and other assemblyapplications. Particular examples include: baby diaper leg elastic,diaper frontal tape, diaper standing leg cuff, diaper chassisconstruction, diaper core stabilization, diaper liquid transfer layer,diaper outer cover lamination, diaper elastic cuff lamination, femininenapkin core stabilization, feminine napkins adhesive strip, industrialfiltration bonding, industrial filter material lamination, filter masklamination, surgical gown lamination, surgical drape lamination, andperishable products packaging. Suitable embodiments of woodworkingapplications comprise 30–50 wt % polyolefins, preferably an EVA, 15–35wt % resins as described herein, and 20–50 wt % fillers, such as calciumcarbonate, barium sulfate, silica or titanium dioxide. Suitableembodiments of bookbinding applications include 35–45 wt % polyolefin,preferably an EVA, 35–45 wt % resin as described herein, and 10–25 wt %wax.

The adhesives and adhesives chosen by the methods described herein areespecially useful in articles having an adhesive bond, in particular, inarticles having at least one bonded surface that may be classified as adifficult substrate. Such substrates generally have low energy(non-polar and/or smooth) surfaces. Examples include, but are notlimited to, fluorinated surfaces, such as fluorinated paper,polyolefinic surfaces, e.g., polyethylene, polypropylene, acrylic-coatedpapers, polymers, and films, and PET. Typical articles that may includesuch substrates are packaging films, cartons, boxes and cases, cerealboxes, and packaging innerliners, e.g., pet food bag innerliners.

EXAMPLES

Properties and Test Methods

In the following examples, Hot Melt Adhesives (HMAs) were prepared asfollows. The components of the HMA formulation were introduced in aZ-blade mixer previously heated to 180° C. under nitrogen blanketing.Any waxes or other components were introduced after 10 minutes, and themixing was continued for another 60 min. The mixer was stopped, thenitrogen blanket was removed, and the blend was poured into a tray madefrom standard release paper. The blend was further cooled under nitrogenblanket and covered with release paper.

HMA formulations were made with the components and their parts by weightlisted in the relevant tables below. Tackifier 1 was athermally-polymerized hydrogenated aromatic-containing DCPD resingrafted with 2.5 wt % maleic anhydride (Saponification No. 25 gm KOH/gresin, Softening Point 94° C.). Tackifier 2 was Sylvalite™ RE 100 talloil rosin ester available from Arizona Chemical Company (softening point96° C., Mn 950, Mw 1110, Saponification No. 26). Tackifier 3 was athermally-polymerized hydrogenated aromatic-containing DCPD resin(available as Escorez™ 5600 from ExxonMobil Chemical Company having asoftening point of 103° C., Mn 270, and Tg 55° C.). The EVA was EscoreneUL 40028 ethylene vinyl acetate copolymer having a MI of 400 g/10 min, adensity of 0.947 g/cm³ and a vinyl acetate content of 28 % availablefrom ExxonMobil Chemical Company. The other components were:

Component Description Source Irganox ™ 1010 Phenolic antioxidantCiba-Geigy Np Wax PARAFFIN WAX 68° C. TotalElfAtoFina Normal paraffin(Np) wax (Melting point 68° C.) FT Wax PARAFLINT H1, Schumman-SasolFischer Tropsch polyethylene wax

The samples were prepared for the AFM analysis as follows. A series ofcardboard substrates were cut into 2.5 cm×7.5 cm strips and weighed. TheHMA formulations were made as previously described and heated to 170° C.in glass tubes placed in a heated aluminum block. When the HMA wasmolten, a warm glass eyedropper was used to apply a drop of adhesive ofapproximately 3 mm diameter (approximately 0.1 to 0.15 g) to thecardboard. A strip of polyethylene-co-tetrafluorethylene (500 μm thick),obtained from the DuPont Company under the trade name of Tefzel 500CLZ,was immediately applied to the cardboard having the adhesive thereon. Aweight of 378 g was placed on top of the assembly for approximately 30seconds. The weight was made of stainless steel and its bottomdimensions were 5.5 cm×8.5 cm so that it covered the assembled structurecompletely. The assembled structure was then weighed to determine theamount of adhesive between the substrates. The specimens were then leftfor at least 24 hours before further manipulation/evaluation.

The Tefzel film was gently peeled off the surface, and a section of theadhesive with a smooth surface was selected for examination.

Atomic Force Microscopy (AFM) also known as Scanning Force Microscopy(SFM) was used for surface analysis with high spatial resolution. Aresolution of about 10 nm was used. AFM is used to investigate polymersurfaces where an intermittent contact mode is used because of the softpolymer surface. The method uses high mechanical frequencies (>100 kHz)to “tap” the polymer surface (tapping mode). AFM has been used tosuccessfully image the surfaces of PSAs (Döring, A., Stahr, J., Zollner,S., 23rd Ann tech Seminar Proc, Pressure Sensitive Tapes for the NewMilleneum, New Orleans, La., May 3–5, 2000). The AFM may be and wasoperated in “pulsed force” mode (PFM) in which the probe tip contactsthe polymer surface for a very short time (100 μs), and its downward andupward motions are detected and analyzed to give values for bothstiffness and pull-force of the surface. (Döring, A., PhD Thesis,University of Ulm, 2001, Döring, A., Hild, S., Schroth, K., Paper 33 atthe Rubber Division meeting of the ACS, Savannah, Ga., Apr. 29–May 1,2002). (To achieve results for a pressure sensitive adhesive (notevaluated in these examples), the adhered structure having the adhesiveto be evaluated should be immersed in liquid nitrogen for 5 minutesbefore removal of the Tefzel film.)

For the examples described herein, a cryo-faced surface was prepared bycooling down the sample to −150° C. and cutting a flat surface parallelto the adhesive surface that had been in contact with the Tefzel film bycutting off about a 1 μm layer of adhesive. The surface layer was cutusing a diamond knife (Reichert-Jung™ cryo-microtome) and removed.

The remaining cryo-faced surface was mapped/investigated using a PARK M5AFM equipped with a WiTec™ PFM attachment. Pull-off force and stiffnessimages were recorded for a 3×3 μm area using a point probe fromNanosensor™ (Force Modulation Reflect Coated, force constant of 1.2–5.5N/m), a frequency of 280–304 Hz, an amplitude of 13–14% and a set pointof 1 nN. The PFM generated a set 3×3 μm image file which was subject tofurther processing.

As shown in the Figures, the images show light and dark domains (invarying gray scale 256 levels), corresponding to domains of high and lowpull-off force (adhesion) or high and low stiffness. To quantify thearea of the domains, the following image analysis procedure was used,using functions that are commonly available in the AFM control softwareand standard image processing software, such as Adobe Photoshop™ version6, with Image Processing Tool Kit version 5.2 available from ReindeerGames, Inc.

-   1. A PFM image (3×3 microns) generated during the PFM analysis was    flattened to remove artifacts such as intensity shifts between    adjacent scan lines.    FIGS. 1–6 are the result of step 1.-   2. A 1-pixel Median Filter was applied to the PFM image to suppress    instrument noise from the PFM analysis.-   3. The image contrast was normalized using an Auto-Contrast    function.-   4. The domains with low image intensity (low stiffness domains or    low pull off force domains) were selected by setting a binary    threshold at 20% of the full intensity scale (grayscale level 51    gray and below for an image with 256 levels of gray). The size of    the low intensity domains was determined, using the IP_Features    function of the Image Processing Tool Kit, which also produces a    list of the low-intensity domain area measurements.    FIGS. 13 and 15 illustrate typical results one might obtain from    step 4 (based on Comparative Example 2).-   5. The domains with high image intensity (high stiffness or high    pull-off force) are selected by setting a binary threshold at 80% of    the full intensity scale (grayscale level 205 and above for an image    with 256 levels of gray). The size of the high intensity domains was    determined, using the IP_Features function of the Image Processing    Tool Kit, which also produces a list of the high intensity domain    area measurements.    FIGS. 14 and 16 illustrate typical results one might obtain from    step 5 (based on Comparative Example 2).-   6. The data sets/lists of high and low intensity domain areas from    steps 4 and 5 were combined, and domains smaller than 100 nm² were    removed because they are of the same order of magnitude as the AFM    probe tip.-   7. The overall average domain area for a given domain (3×3 μm) is    then calculated by averaging the values generated in the combined    data sets from step 6.

8. Average domain areas could also be calculated for: the low intensitydomains by averaging the values generated in step 4; and/or the highintensity domains by averaging the values generated in step 5.

Domain Distribution

The homogeneity or domain distribution of a particular sample iscalculated as follows. First, a 3×3 μm image was generated uponcompletion of step 4 to evaluate the low intensity domains. Another 3×3μm image was generated upon completion of step 5 to evaluate the highintensity domains. Each image was then divided into quadrants (1.5×1.5μm) as follows (not to scale):

1 2 3 4

Steps 6 and 7 were then conducted on each quadrant, including combiningthe data sets to generate the average values of the domain areas. Theresulting average domain area for each quadrant was then compared to theoverall average domain area for the overall 3×3 μm image as generated bystep 7 above. The quadrant domain area difference is calculated asfollows (expressed as a percentage):

$\frac{A_{Q} - A_{S}}{A_{S}} \times 100$where A_(Q) is the average domain area for the quadrant, and A_(S) isthe average domain area for the overall 3×3 μm sample area.

The overall average domain distribution is the average of each domainarea difference and is expressed as a percentage. It may be calculatedfor both pull-off force domains and stiffness domains.

TABLE 1 Formulations of Adhesives without Wax Example 2 3 1(Comparative) (Comparative) Formulations (parts by weight) Tackifier 145 0 0 Tackifier 2 0 45 0 Tackifier 3 0 0 45 EVA 35 35 35 Irganox ™ 10100.5 0.5 0.5 Stiffness Overall Average Domain Area (nm²) 1364 2961 4692Average High Intensity Domain Area (nm²) 1402 2765 6056 Average LowIntensity Domain Area (nm²) 1303 3140 3365 Average Domain Area forQuadrant 1 (nm²) 1301 3046 2028 Quadrant domain average area difference(%) 5 −3 57 Average Domain Area for Quadrant 2 (nm²) 1398 2593 6335Quadrant domain average area difference (%) −3 12 −35 Average DomainArea for Quadrant 4 (nm²) 1188 2740 3819 Quadrant domain average areadifference (%) 13 7 19 Pull-Off Force Overall Average Domain Area (nm²)597 983 6275 Average High Intensity Domain Area (nm²) 539 937 5098Average Low Intensity Domain Area (nm²) 713 1163 2499 Average DomainArea for Quadrant 1 (nm²) 625 1117 5491 Quadrant domain average areadifference (%) −5 −14 12 Average Domain Area for Quadrant 2 (nm²) 563828 5876 Quadrant domain average area difference (%) 6 16 6 AverageDomain Area for Quadrant 4 (nm²) 579 817 5099 Quadrant domain averagearea difference (%) 3 17 19

FIGS. 1 to 6 show the adhesive phase structures without the wax wherethe polymer/tackifier phase structures can be analysed without theinterference of the wax crystals. The images show the cryo-microtomedsurfaces as described herein. The formulation containing Tackifier 1(FIGS. 1 and 2) has the smallest domains, the least variation in thesizes of the domains and the most even distribution of the domains,which is indicative of the best adhesive performance. The formulationcontaining Tackifier 2 (FIGS. 3 and 4) has bigger domains less evenlydistributed throughout the matrix, which is indicative of inferiorperformance. The formulation containing Tackifier 3 (FIGS. 5 and 6) haslarge stiffness/adhesion domains which are irregularly distributedthroughout the image.

In Examples 4–6, AFM images in “tapping mode” were generated as shown inFIGS. 7–12, based on the formulations shown in Table 2. The images wereflattened and subjected to noise reduction using a 2-pixel MedianFilter.

TABLE 2 Adhesives with Wax Example 5 6 Formulation (parts by weight) 4(Comparative) (Comparative) Tackifier 1 45 0 0 Tackifier 2 0 45 0Tackifier 3 0 0 45 EVA 35 35 35 Np Wax 10 10 10 FT Wax 10 10 10Irganox ™ 1010 0.5 0.5 0.5

FIGS. 7 to 12 show a fully formulated HMA containing an EVA copolymer,tackifier, waxes and antioxidant as described in Table 2. The AFM imagesshow the surface of the adhesive that was in contact with the Tefzelfilm. The topography images (FIGS. 7, 9 and 11) and phase shift images(FIGS. 8, 10 and 12) clearly show the surfaces of the formulations. Theimages (FIGS. 11/12) illustrating the formulation with Tackifier 3 inExample 6 are dominated by large wax crystal structures which adverselyaffect the surface adhesion. The images showing the formulationcontaining Tackifier 2 in Example 5 (FIGS. 9/10) illustrate animprovement over the formulation containing Tackifier 3 because the waxcrystals are less prominent, but they still appear to adversely affectthe surface adhesion. In the formulation containing Tackifier 1 inExample 4, the images (FIGS. 7/8) illustrate that the wax crystals areless prominent, and therefore, do not affect the surface adhesionadversely as indicated in Examples 5 and 6.

Various tradenames used herein are indicated by a ™ symbol, indicatingthat the names may be protected by certain trademark rights. Some suchnames may also be registered trademarks in various jurisdictions.

All, patents, test procedures, and other documents cited herein,including priority documents, are fully incorporated herein by referenceto the extent such disclosure is not inconsistent with this inventionand for all jurisdictions in which such incorporation is permitted.

1. A method for selecting an adhesive composition having improvedperformance, the method comprising observing a surface with an atomicforce microscope, characterized in that the surface is anon-destructively de-bonded surface of the adhesive composition, andthat the method further comprises (a) subdividing the de-bonded surfaceinto domains of pull-off force or stiffness; and (b) selecting anadhesive composition having (i) an average stiffness domain area lessthan about 2500 nm²; or (ii) an average pull-off force domain area lessthan about 2500 nm²; or (iii) a pull-off force overall average domaindistribution less than about 25%; or (iv) a stiffness overall averagedomain distribution less than about 25%; or (v) combinations of any twoor more thereof.
 2. The method of claim 1 comprising selecting anadhesive composition having at least two of parameters (i)–(iv).
 3. Themethod of claim 2 comprising selecting an adhesive composition having atleast three of parameters (i)–(iv).
 4. The method of claim 3 comprisingselecting an adhesive composition having all of parameters (i)–(iv). 5.A method for selecting an adhesive composition, the method comprising:(a) observing a non-destructively de-bonded surface of the adhesivecomposition; (b) subdividing the de-bonded surface into domains of atleast one of pull-off force or stiffness; and (c) selecting an adhesivecomposition having at least one of the following parameters: (i) anaverage stiffness domain area less than about 2500 nm²; (ii) an averagepull-off force domain area less than about 2500 nm²; (iii) a pull-offforce overall average domain distribution less than about 25%; or (iv) astiffness overall average domain distribution less than about 25%. 6.The method of claim 5 comprising selecting an adhesive compositionhaving at least two of parameters (i)–(iv).
 7. The method of claim 6comprising selecting an adhesive composition having at least three ofparameters (i)–(iv).
 8. The method of claim 7 comprising selecting anadhesive composition having all of parameters (i)–(iv).